To provide a method for preparing a mayenite type compound having electroconductivity imparted.A method for preparing an electroconductive mayenite type compound, which comprises melting a raw material containing Al and at least one element selected from the group consisting of Ca and Sr, holding the melt in a low oxygen partial pressure atmosphere having an oxygen partial pressure of not higher than 10 Pa, followed by cooling or annealing in a low oxygen partial pressure atmosphere or in atmospheric air for solidification, thereby to replace oxygen present in cages by electrons in a high concentration.